Other faithful said the saw the deceased preparing himself for prayers at a nearby mosque and later found his body lying in a pool of blood.
Witnesses said they saw two motorcycles speeding away from the scene.
Area MCA Abdirizak Ismail said this is the third grisly murder of a night guard in Garissa town in three weeks.
"Police should intensify patrols. Interior CS Fred Matiang’i should declare a shoot to kill order for robbers to tame runaway crime," he said.
The MCA urged residents to desist from shielding suspects because they come from their clan.
A worker at the hardware store accused boda boda riders of colluding with criminals.
Police are scrutinising CCTV footage at the hardware so as to identify the killers.
Nothing was stolen from the shop. The suspects cut the grills and gained entry into the hardware. However, they were unable to break the safe.